112_vonkomer.pdf

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FAST AC ELECTRIC DRIVE DEVELOPMENT PROCESS

USING SIMULINK CODE GENERATION POSSIBILITIES

Jakub Vonkomer, Tatiana Radiov, Milan alman, Miroslav Suchnek

Institute of Control and Industrial Informatics,

FEI STU Ilkovi

ova 3, 812 19 Bratislava, Slovak [email protected]

Abstract

Vector control is essential part of any modern AC drive. Therefore development of

high performance vector control of induction machine is presented. Vector control

algorithms described in this paper have been intensively tested in the Simulink

environment with SimPowerSystems toolbox and later on a real 1.1 kW induction

machine using dSpace controller board as well. Schemas and screen captures of the

models are included. Design of the controllers and flux observer is described. Finally

the comparison of results between simulation and real motor is presented.

Index terms AC drive, vector control, speed control, dSpace, current controllers,

flux controller, Simulink, SimPowerSystems

Introduction

The development process of electric drives is usually very time-intensive itself and it also takesa lot of time to transform the model to the final code. Manual code writing of the model introduces alot of bugs and errors. Some of the bugs even require many hours to be fixed. But nowadays there isno need to do it this way, because of MATLAB code generation possibilities. In our case we used theReal Time Workshop for generating code for dSpace. The generated C code is then compiled anddownloaded to the dSpace processor and can be immediately executed. However there are more

supported targets for Simulink code generation (TI C2000, Freescale MPC5xx ). This process ofdesign and development is called model based design.

Vector Control

Vector control allows high performance control of electromechanical variables like torque,speed, position in both static and transient states. Main task for vector control is direct control ofmagnetic flux and torque. There are plenty of methods of vector control but we focus on rotor-flux-oriented vector control. The vector control basis can be derived from

srmm ikM = Wherer

mm L

Lpk =

2

3 (1)

Scalar form of previous equation

sinsrmm ikM = (2)

is1

Si

is2 r

Figure 1 - Vector diagram of stator current and rotor magnetic flux
mailto:[email protected]:[email protected]:[email protected]


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2

s

1Si r

is2 is1

Figure 2 - Vector diagram of the IM state variables

Figure 3 - Simplified flow chart of vector control

All the controllers and observers are derived from the mathematical model of the inductionmachine:

sks

sss jdtdiRu ++=

(3)

rslr

rr jdt

diR

0 ++=

(4)

}{2

3 *rs

r

mm iL

LpM =

(5)

mp'= (6)

dtJMM lmd

=

si

su

r

(7)

Table 1 - Description of symbols and acronyms used in this paper:

- angular speed of motorsl - slip speed

p - number of pole pairsLs - stator leakage inductanceLs - stator winding inductanceLr - rotor winding inductanceLm - mutual inductanceRs - stator resistance

Rr - rotor resistanceR1 - combined resistance (R1=Rs+Lm

2/Lr2*Rr)

T1 - current model time constant (T1=Ls/R1)Tr - rotor time constant (Tr=Lr/Rr)J - moment of inertiaMm - motor torqueMl - load torque

- stator current vector

- stator voltage vector

- rotor flux vectors - stator flux vector


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The structure type of all controllers is PI and they are designed by using pole-placementmethod. All systems are described by first order dynamic equations.

Current controllers

Design of current controllers is derived from the following transfer function:

( )

( )

( )

( )

( ) 1121 +===

sTsususG

SSS

/1 121 Rsisi SS

o

(8)

Final current controller parameters are achieved using the following equations:( is desired dynamics, desired damping)b

11

12 TRbK op

= 1T

2p

i

KT =

( ) ( )

( )

11 oTR (9)

Flux controller

Design of flux controller is derived from transfer function:

11 +=

=

sT

L

si

ss

r

m

S

rSG

(10)

Final current controller parameters

mrr

op L

T

TbK

=1

2

2or

mpi

T

LK

=

( ) ( )

( )

T

(11)

Speed controller

Speed controller is designed by knowing the mechanical parameters

Transfer function:

BJsL

Lp

si

ssG r

r

m

SS +

==1

'2

3

1

(12)

Final equations:

( )2

'2

3

o

rr

mp

iJ

L

LpK

T

=

r

rL

m

op L

p

BJbK

=

'32

2

(13)

Flux weakening controller

Flux weakening is necessary for achieving speeds higher than rated speed of the motor. Thedesign of flux weakening controller is too complicated for this paper. But in general it is voltagecontroller which is activated when the voltage is close or equal to saturation.

Flux observer

Flux observer is the heart of vector control, because of the control algorithm is oriented in rotormagnetic flux reference frame. That is one of the reasons vector control is often called Field OrientedControl.

is mechanical angular speed,Following equations and figure 4 describes presented flux observer. is mechanical rotor position (time integral of ).


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Figure 6 - Inner connection of the VECTOR CONTROL block

Figure 7 - Inner connection of the inverter block

Figure 8 - Inner connection of the current controller block

dSpace model

The dSpace board allows real-time control of different systems. Its main advantage isintegration into the MATLAB/Simulink environment. So instead of complicated time-intensiverewriting model to the C code, we developed the program in Simulink and then we just built andexecuted the finished model. Model is executed and controlled via the ControlDesk application. It isalso very easy to export any graphs to MATLAB.


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Figure 9 Screen capture of proposed dSpace model

DSpace models and simulation models are pretty similar as can be seen in figure 9. Instead ofinduction machine and inverter blocks, the block of communication with inverter is used. Inputsrepresent reference voltages. The block of communication with inverter contains the compensation ofDC voltage fluctuations as well and the computed duty cycles are inputs for the dSpace PWM block.

Figure 10 shows the basic schema of connection dSpace controller board to frequencyconverter and the induction machine as well.

Figure 10 Schema of connecting dSpace equipped PC with frequency inverter and induction motor


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Comparison

Figures 11-14 show the comparison of simulation and real behaviour of modelled system.Vector control at low speed is demonstrated. Small differences and noise in dSpace figures are caused

by non-calibrated current sensors, but indeed we can say that we reached comparative results withinthe toleration.

0 0.5 1 1.5 2 2.5 3 3.5 4-20

0

20

40

60

80

100

120Speed: dSpace - w* = 0-20-40-60-80-100 rad/s

time [s]

angularspeed

[rad/s]

measured

reference

Figure 11 dSpace experiment: steps of reference speed up to 100 rad/s

0 0.5 1 1.5 2 2.5 3 3.5 4-20

0

20

40

60

80

100

120

time [s]

angularspeed

[rad/s]

Speed: Simulation - w* = 0-20-40-60-80-100 rad/s

measured

reference

Figure 12 Simulation: steps of reference speed up to 100 rad/s


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0 0.5 1 1.5 2 2.5 3 3.5 4-15

-10

-5

0

5

10

15Speed: dSpace - w* = 10 rad/s to -10 rad/s

time [s]

angularsp

eed

[rad/s]

measured

reference

Figure 13 dSpace experiment: performance of low speed and speed reversal

0 0.5 1 1.5 2 2.5 3 3.5 4-15

-10

-5

0

5

10

15

time [s]

angularspeed

[rad/s]

Speed: Simulation - w* = 10 rad/s to -10 rad/s

measured

reference

Figure 14 Simulation: performance of low speed and speed reversal

Conclusion

In this paper we had focus on induction machine vector control development. Since thebeginning we tried to keep the model simple, robust and fully discrete as well, because we planned toshare the basic model with other platforms dSpace in our case. The basic testing during the creationand development of the model was by simulation only, later we tried it also on a dSpace platformwhere real capabilities were demonstrated.

In the future we may use another platform and it can be used for educational purposes and alsofor testing some advanced control structures.

Acknowledgement

This work has received support from the Slovak Research and Development Agency. Project referencenumber is APVV-0530-07.


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References

[1]

alman M.: Akn leny (Slovak language), STU Bratislava 2003

[2]Milan alman lectures for Inteligent Servosystems, 2007/2008.http://servo.urpi.fei.stuba.sk/index.php?option=com_content&task=view&id=15&Itemid=26

[3]

Doki, S.; Kinpara, Y.; Okuma, S.; Sangwongwanich, S., "Unified interpretation of indirect

and direct vector control [of electric machines],"Power Conversion Conference, 1993.Yokohama 1993., Conference Record of the, vol., no., pp.297-302, 19-21 Apr 1993URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=264167&isnumber=6639

[4]DS1104 R&D Controller Board, dSpace Inc. 2009 Catalogue,URL:http://www.dspaceinc.com/ww/en/inc/home/medien/papers/download_page.cfm?FileID=778

[5]

The MathWorks, SimPowerSystems Documentation, 2008URL:http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/

[6]

The MathWorks, SimPowerSystems Demos, 2008

Ing. Jakub Vonkomer, Email:[email protected]

Ing. Tatiana Radiov, Email: [email protected]

prof. Ing. Milan alman PhD, Email: [email protected]

Ing. Miroslav Suchnek, Email: [email protected]

Institute of Control and Industrial Informatics, Faculty of Electrical Engineering and InformationTechnology, Slovak University of Technology in Bratislava,
http://servo.urpi.fei.stuba.sk/index.php?option=com_content&task=view&id=15&Itemid=26http://servo.urpi.fei.stuba.sk/index.php?option=com_content&task=view&id=15&Itemid=26http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=264167&isnumber=6639http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=264167&isnumber=6639http://www.dspaceinc.com/ww/en/inc/home/medien/papers/download_page.cfm?FileID=778http://www.dspaceinc.com/ww/en/inc/home/medien/papers/download_page.cfm?FileID=778http://www.dspaceinc.com/ww/en/inc/home/medien/papers/download_page.cfm?FileID=778http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/http://www.dspaceinc.com/ww/en/inc/home/medien/papers/download_page.cfm?FileID=778http://www.dspaceinc.com/ww/en/inc/home/medien/papers/download_page.cfm?FileID=778http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=264167&isnumber=6639http://servo.urpi.fei.stuba.sk/index.php?option=com_content&task=view&id=15&Itemid=26

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112_vonkomer.pdf